Animation of proportional editing deformation (cylinder to figure eight)
You can do it the other way around:

Create your 8 shape:





Once you are good, in Object mode, create a basic shapekey and a second shapekey:



Keep the second shapekey selected and in Edit mode, select all and right click &gt; LoopTools &gt; Circle:




Back in Object mode, use the shapekey Value to morph from the circle to the 8 shape: